Computer implemented system and method for storing data on a blockchain

ABSTRACT

A method of storing data on a blockchain, such as the bitcoin blockchain, is disclosed. The method comprises generating a blockchain transaction having at least one first input and/or at least one first output containing first data (&lt;Content 1&gt;) to be stored on the blockchain, and at least one second input and/or at least one second output containing second data (&lt;Attribute 1&gt;,&lt;Attribute 2&gt;) representing at least one attribute of the first data. At least one second input and/or at least one second output is separate from the or each first input and/or first output.

This invention relates generally to cryptographic techniques forimproved data communication and exchange across an electronic network,and in particular a peer-to-peer network such as a blockchain network.It relates to data storage, access, retrieval and processing, and moreparticularly to such data-related activities on a blockchain. Theinvention is particularly suited, but not limited to, use in processingdata in a manner similar to that provided by web sites and web pages butusing the blockchain as an underlying mechanism or platform rather thanweb server(s). Thus, the invention provides a secure, efficient,cryptographically-enforced, alternative infrastructure for dataprocessing and transfer.

In this document we use the term ‘blockchain’ to include all forms ofelectronic, computer-based, distributed ledgers. These includeconsensus-based blockchain and transaction-chain technologies,permissioned and un-permissioned ledgers, shared ledgers and variationsthereof. The most widely known application of blockchain technology isthe Bitcoin ledger, although other blockchain implementations have beenproposed and developed. While Bitcoin may be referred to herein for thepurpose of convenience and illustration, it should be noted that theinvention is not limited to use with the Bitcoin blockchain andalternative blockchain implementations and protocols fall within thescope of the present invention. The term “user” may refer herein to ahuman or a processor-based resource. “Bitcoin” as used herein includesall versions and variations of protocols which derive from the Bitcoinprotocol.

A blockchain is a peer-to-peer, electronic ledger which is implementedas a computer-based decentralised, distributed system made up of blockswhich in turn are made up of transactions. Each transaction is a datastructure that encodes the transfer of control of a digital assetbetween participants in the blockchain system, and includes at least oneinput and at least one output. Each block contains a hash of theprevious block so that blocks become chained together to create apermanent, unalterable record of all transactions which have beenwritten to the blockchain since its inception. Transactions containsmall programs known as scripts embedded into their inputs and outputs,which specify how and by whom the outputs of the transactions can beaccessed. On the Bitcoin platform, these scripts are written using astack-based scripting language.

In order for a transaction to be written to the blockchain, it must be“validated”. Network nodes (miners) perform work to ensure that eachtransaction is valid, with invalid transactions rejected from thenetwork. Software clients installed on the nodes perform this validationwork on an unspent transaction (UTXO) by executing its locking andunlocking scripts. If execution of the locking and unlocking scriptsevaluate to TRUE, the transaction is valid and the transaction iswritten to the blockchain. Thus, in order for a transaction to bewritten to the blockchain, it must be i) validated by the first nodethat receives the transaction—if the transaction is validated, the noderelays it to the other nodes in the network; and ii) added to a newblock built by a miner; and iii) mined, i.e. added to the public ledgerof past transactions.

Although blockchain technology is most widely known for the use ofcryptocurrency implementation, digital entrepreneurs have begunexploring the use of both the cryptographic security system Bitcoin isbased on and the data that can be stored on the Blockchain to implementnew systems. It would be highly advantageous if the blockchain could beused for tasks and processes which are not limited to the realm ofcryptocurrency. Such solutions would be able to harness the benefits ofthe blockchain (e.g. a permanent, tamper proof records of events,distributed processing etc) while being more versatile in theirapplications.

One such area of interest is the use of the blockchain for the storage,sharing, accessing and controlling of data among users. Today, this isachieved via the Internet, with servers hosting web sites and pageswhich users visit in order to access the desired data, typically with asearch engine.

However, some observers have begun to envisage the use of the blockchainto address some of the disadvantages of the Internet, such as control oflarge amounts of data and content by centralised parties. See, forexample, “Life After Google: The Fall of Big Data and the Rise of theBlockchain Economy”, George Gilder, Gateway Editions, July 2018,ISBN-10: 9781621575764 and ISBN-13: 978-1621575764.

Thus, it is desirable to provide an arrangement enabling such data to bestored, processed, retrieved, searched and/or shared on the blockchain,advantageously utilising the distributed, unalterable, distributed andpermanent nature of the blockchain. Such an improved solution has nowbeen devised.

Embodiments of the present disclosure provide, at least, alternative,efficient and secure techniques for implementing a blockchain solutionand for storing, processing, searching and/or retrieving data thereon ortherefrom. Embodiments also provide, at least, an alternative,blockchain-implemented technical infrastructure for storing, processing,retrieving, transferring, searching and/or sharing data betweencomputing nodes. Because the invention enables the blockchain network tobe used in a new way and for the provision of an improved and technicalresult, the invention provides an improved blockchain-implementednetwork.

Embodiments also provide solutions for the secure control of access todigital resources over a technically different and improved computingplatform which comprises a blockchain and a blockchain protocol.

The invention is defined in the appended claims.

In accordance with the invention there may be provided a computerimplemented method.

It may be a method of storing data on a blockchain, the methodcomprising:

-   -   generating a blockchain transaction having at least one first        input and or at least one first output containing first data to        be stored on the blockchain, and at least one second input and        or at least one second output containing second data        representing at least one attribute of said first data, wherein        at least one said second input and or at least one said second        output is separate from the or each said first input and or        first output.

By storing the first data separately from the second data representingat least one attribute of the first data, this provides the advantage ofenabling data to be stored on a blockchain in a manner independent ofthe protocol used to process the data, thereby making the process moreuniversally applicable. In addition, separating the first data and thesecond data provides the advantage of enabling the first data to be morereadily digitally signed by a third party. Also, the explicit separationof the data attributes and content provides a standardised procedure fordata insertion in the blockchain. This captures both existing datainsertion methods as well as offering support for future extensions. Inaddition, once the data is inserted on the blockchain, it can have aunique identifier and location. This removes the onus on a user tolocally store a copy of the data as it is immutable once included on theblockchain. This also means that the data is retrievable by a user atany point in time without the need for any disaster recovery mechanism.

The first data may be contained in a plurality of said first inputs andor said first outputs.

By storing the first data in a plurality of first inputs and/or firstoutputs, this provides the advantage of enabling the density of datastorage in the transaction to be maximised.

Said second data may include data relating to recombination of saidfirst data.

At least one said second input and or at least one said second outputmay include indication data indicating that the transaction includessaid first data.

This provides the advantage of avoiding unnecessary processing ofblockchain transactions not including the first data, thereby improvingefficiency of processing.

The second data may represent at least one attribute of said first data,being at least one of data type, data encryption scheme, datacompression scheme, indexing information, permission information,encoding information, keyword information or searching information ofsaid first data.

The first data may be contained in at least one said first output.

This provides the advantage of enabling validity of the transaction tobe checked as part of the blockchain mining process. Data integrity isensured through the existing miner validation process of the underlyingblockchain. This allows the blockchain to be used as a trusted globalserver where the integrity of the stored data is guaranteed by theminers and thus can be stored and distributed by other parties withoutthe need for trust.

At least one said first and/or second output may include a script opcodefor marking an output as invalid for subsequent use as an input to asubsequent transaction.

This provides the advantage of avoiding processing of the output as partof the unspent transaction output (UTXO) data, thereby improvingefficiency of processing.

At least one said first and/or second output may be spendable.

This provides the advantage of enabling executable programs to beincluded in the first data, which could otherwise be prevented fromoperating in an unspendable output, for example as a result of anOP_RETURN operator. The OP_RETURN operator also has the added advantageof terminating the executable program.

At least one said first output may be redeemable by means of least onekey corresponding to a respective digital signature applied to saidfirst data.

This provides the advantage of utilising the process of verifying ofdigital signatures of the transaction, carried out as part of thecryptocurrency mining process to verify that the transaction is valid,to further verify validity of the first and/or second data.

A digital signature may be applied to said first data.

This provides the advantage of enabling the first data to be morereadily isolated from the second data and digitally signed by a thirdparty independently of the second data, thereby making the process moreuniversally applicable, and enabling faster data processing. This alsoenables the method to be made more protocol-independent.

At least one said digital signature may be based on a cryptographysystem having a public-private key pair, wherein the private key isbased on a plurality of prime numbers and the corresponding public keyis based on a product of a plurality of said prime numbers.

This provides the advantage of providing signature schemes which arecomputationally inexpensive to verify, thereby improving efficiency ofprocessing.

At least one said digital signature may be a Rabin signature.

This provides the advantage that a distributor can provideauthentication from the original source of the data using Rabinsignatures. This allows the content itself to be signed for by theoriginal author to prove its authenticity.

The method may further comprise applying data compression to said firstdata and/or said second data.

The invention also provides a system, comprising:

-   -   a processor; and    -   memory including executable instructions that, as a result of        execution by the processor, causes the system to perform any        embodiment of the computer-implemented method described herein.

-   The invention also provides a non-transitory computer-readable    storage medium having stored thereon executable instructions that,    as a result of being executed by a processor of a computer system,    cause the computer system to at least perform an embodiment of the    computer-implemented method described herein.

These and other aspects of the present invention will be apparent fromand elucidated with reference to, the embodiment described herein. Anembodiment of the present invention will now be described, by way ofexample only, and with reference to the accompanying drawings, in which:

FIG. 1 shows a blockchain transaction embodying the present invention inwhich data is stored in a plurality of outputs;

FIG. 2 shows a blockchain transaction embodying the present invention inwhich data is stored in an input;

FIG. 3 shows a series of blockchain transactions embodying the presentinvention in which data is stored over outputs of a plurality ofblockchain transactions;

FIG. 4 shows a blockchain transaction embodying the present inventiontransferring cryptocurrency payment to allow access to data by means ofan atomic swap;

FIG. 5 shows a blockchain transaction embodying the present inventionfor redeeming the payment of the transaction of FIG. 4;

FIG. 6 shows secret values kept by participants in a blockchaintransaction embodying the present invention issuing tokens to allowaccess to data by means of an atomic swap;

FIGS. 7 and 8 show blockchain transactions embodying the presentinvention for issuing tokens to allow access to data by means of anatomic swap;

FIGS. 9 and 10 show blockchain transactions embodying the presentinvention for redeeming tokens issued by means of the transactions ofFIGS. 7 and 8;

FIGS. 11 and 12 show blockchain transactions for accessing the secretsexchanged by the transactions of FIGS. 9 and 10;

FIG. 13 provides an illustration of the Metanet graph structure inaccordance with an embodiment of the present invention.

FIG. 14 shows an illustration of a Metanet graph tree for the domain‘bobsblog’ including MURL search paths in accordance with an embodimentof the present invention.

FIG. 15 shows a schematic for an illustrative embodiment of abrowser-wallet in accordance with one example of the invention, and howits core functions can be split across different components of theapplication.

FIG. 16 provides a diagram illustrating how searching for content can beperformed within the infrastructure of an embodiment of the invention.

FIG. 17 shows an illustrative interaction between local- and global-fullcopy peers in accordance with an embodiment of the invention.

FIG. 18 shows a Metanet a tree (or graph) for use in reference to theillustrative use case described below.

FIG. 19 shows a flow chart which illustrates the process embodied by theillustrative use case provided below.

FIG. 20 is a schematic diagram illustrates a computing environment inwhich various embodiments can be implemented.

The term “bitcoin” is used herein for convenience only, and is intendedto include all cryptocurrency/blockchain protocols including, but notlimited to, all variations that are derived from the Bitcoin protocol aswell as any alternative protocols for other blockchains. In theremainder of this document, the protocol determining operation of theembodiments of the present invention will be referred to as the “Metanetprotocol”. The terms “content” and “data” may be used interchangeablyherein to refer to data that is stored in a blockchain transaction inaccordance with embodiments of the present invention.

Overview

As stated above, there is a recognised need for an improved and/oralternative infrastructure for storing, writing, accessing and reviewingdata between and by computing nodes. It would be advantageous to use thebenefits which are inherent with blockchain technology (e.g. immutablerecords, cryptographically enforced control and access, built-in paymentmechanism, ability to publicly inspect the ledger, distributedarchitecture etc). However, the construction of a “blockchainimplemented internet” is challenging from a number of technicalperspectives.

These challenges may include, but are not limited to: how to locate aparticular portion of data within the network; how to secure and controlaccess to the data so that only authorised parties may gain access; howto transfer the data from one party to another in a per-to-peer manner;how to arrange the data so that it can be logically associated yetstored in different locations within the network and how to subsequentlycombine it from different locations to provide a collective andaugmented result; how to provide and/or store data in a hierarchicalfashion; how to allow users and parties with different computingplatforms access to the desired data; how to store, provide and sharedata across a (potentially global) computing network without reliance onor the need for large storage servers and centralised data controllers,and how to improve the efficiency of such data-related activities on thenetwork.

Herein, “sharing” may include providing to a node or user, sending,communicating, transmitting or providing access to the portion of data.The term “processing” may be interpreted as meaning any activityrelating to the transaction or its associated data, includinggenerating, transmitting, validating, accessing, searching for, sharingsubmitting to a blockchain network, and/or identifying.

The present invention provides such an improved solution in a mannerwhich, in some ways, is analogous to the internet but achieves itsresults in an entirely different way, using an entirely differentplatform of hardware and software components from that known in theprior art. In accordance with embodiments of the present invention, theservers which store internet/web data and provide it to end users arereplaced by blockchain transactions residing on the blockchain network.In order to achieve this, several innovations have had to be devised.These are described in the following sections.

Inserting Data into the Blockchain “Metanet” Referring to FIG. 1, ablockchain transaction embodying the present invention is shown in whichfirst data to be stored on the blockchain is stored in one or more firstoutputs of the transaction, and second data representing attributes ofthe first data is stored in one or more second outputs of thetransaction. One or more first parts <Content 1> of the first data arestored in a spendable output of the transaction. Data <Attribute 1> and<Attribute 2>, representing respective attributes of the first data,together with a flag indicating that data is being stored according tothe Metanet protocol, is stored in a second, unspendable output of thetransaction. The term “unspendable” is used to indicate that at leastone first and/or second output of the transaction may include a scriptopcode (OP RETURN) for marking an output as invalid for subsequent useas an input to a subsequent transaction.

It is advantageous to store the content and attributes parts of the dataseparately in separate outputs of the transaction.

FIG. 2 shows a blockchain transaction embodying the present invention inwhich first data <Content 1> to be stored on the blockchain is stored inan input of the transaction. The Metanet flag, and the attributes data<Attribute 1> and <Attribute 2> are stored in an unspendable output ofthe transaction, in a manner similar to the arrangement shown in FIG. 1.

Data Insertion

Data Insertion Methods

It is desired to be able to insert the following data into theblockchain

-   -   a) Metanet Flag    -   b) Attributes    -   c) Content

The content is data to be stored on the blockchain, the Metanet Flag isa 4-byte prefix that acts as the identifier for any data pertaining tothe Metanet protocol, while the attributes contain indexing,permissioning and encoding information about the content. This couldinclude, but is not limited to, data type, encryption and/or compressionschemes. Such attributes are also often referred to as metadata. Use ofthis term in the present document will be avoided in order to avoidconfusion with transaction metadata.

The following techniques can be used to embed this data within a Bitcoinscript:

-   -   1. OP_RETURN—In this method all data (attributes and content)        are placed after OP_RETURN in the locking script of a provably        unspendable transaction output.

An example of an output script using this operator is:

UTXO0: OP_RETURN <Metanet Flag><attributes><content>

-   -   2. OP_RETURN with OP_DROP—In this case the OP_RETURN contains        the attributes, whilst the content is stored before an OP_DROP        in a spendable transaction script (either locking or unlocking).        The content can be split into multiple data packets within the        transaction input and outputs. However, it is advantageous to        insert data into transaction outputs as it is only output        scripts that may be signed in the Bitcoin protocol. If the data        is inserted into the transaction input, OP_MOD can be used as a        checksum on the data to ensure its validity in place of miner        validation. For example, one could perform a 32-bit OP_MOD        operation and check that it is equal to a pre-calculated value.

In this case, the attributes may contain information about how thecontent data packets are recombined. In addition, providing the hash ofthe recombined data packets H(content1+content2) as an attribute enablesverification that the recommended recombination scheme has been used.

A transaction that implements the second data insertion method is shownin FIG. 1. For simplicity this transaction only includes contentinserted in its outputs, that is signed by its single input. Contentinserted into additional inputs would also be possible using OP_DROPstatements using this method as shown in FIG. 2.

If the content is very large it may be advantageous to split it overmultiple transactions. Such an arrangement is shown in FIG. 3. FIG. 3shows a pair of blockchain transactions embodying the present inventionin which first data <Content> to be stored on the blockchain is splitinto two chunks <Content chunk 1> and <Content chunk 2> which cansubsequently be recombined as <Content>=<Content chunk 1>∥<Content chunk2>, where the operator ‘∥’ concatenates the two chunks of content data.This concatenation operator may be replaced by any desired bitwise orsimilar piecewise binary operator. The two chunks <Content chunk 1> and<Content chunk 2> are then stored in respective spendable outputs of theseparate blockchain transactions, while data relating to the attributesof the content data is stored in respective unspendable outputs of theblockchain transactions. Again, the attributes can contain informationabout the recombination scheme. For example, the content may be rawdata, an executable program or a HTML webpage. Additionally, content1may include a pointer to the location on the blockchain of content2,which functions in the same way as an embedded HTML link within awebpage.

It should be noted that both transactions take the same public key P(and ECDSA signature) as input, such that <Content chunk 1> and <Contentchunk 2> can be related by the same public key P despite being stored indifferent transactions with TxID1 and TxID2 respectively.

Exploiting the Role of Miner Validation

Here the transaction validation process performed by miners is used togain an advantage when storing this data. This is because all data intransaction outputs will be signed by the owner of a public key P in atleast one transaction input (if the SIGHASH|ALL flag is present) andthis signature will be checked in the transaction validation processthat all miners perform.

This ensures

-   -   Data integrity—If the data is corrupted the CHECKSIG operation        will fail.    -   Data authenticity—The owner of P has provably witnessed and        signed the data.

This is particularly advantageous for content that is split overmultiple transactions as the input signature of P provides a provablelink between the split components of the data, as described above withreference to the arrangement is shown in FIG. 3.

Rabin Signature

Another way to ensure data authenticity is to use Rabin signatures,which can be used to sign the data itself rather than the whole message.This can be advantageous as the signer does not need to sign everyindividual transaction in which the data appears, and the signature canbe re-used in multiple transactions.

Rabin signatures can be easily validated in script. These can beincorporated in case (2) above by inserting Rabin signature validationbefore the OP_DROP command, i.e.

-   <content1><Rabin Sig (content1)> FUNC_CHECKRABSIG OP_DROP    <H(P₁)>[CheckSig P₁]

It should be noted that this cannot be done in case (1) above since ascript containing OP_RETURN fails anyway and so no validation can beachieved.

Specific Example of Use of Rabin Signature

Introduction

Digital signatures are a fundamental part of the Bitcoin protocol. Theyensure that any Bitcoin transaction recorded on the blockchain has beenauthorised by the legitimate holder of the Bitcoin being sent. In astandard Bitcoin P2PKH transaction a transaction message is signed usingthe elliptic curve digital signature algorithm (ECDSA). However theECDSA signature is generally applied to the whole transaction.

There are some use cases of the Bitcoin blockchain where a participantfrom outside the network may want to provide a signature for arbitrarydata types which can then be used by network participants. By usingRabin digital signatures any piece of data can be signed—even if itoriginates from outside the Bitcoin blockchain and then placed in one ormultiple transactions.

It will now be shown how data can be signed and verified directly inBitcoin script by utilising the algebraic structures of the Rabincryptosystem

Rabin Digital Signatures

The Rabin Digital Signature Algorithm

Background Mathematics

Definition—Integers mod p

The integers modulo p are defined as the set

_(p):={1,2, . . . ,p−1}

Fermat's Little Theorem

Let p be a prime number. Then for any integer a the following applies

a ^(p-1)≡1 mod p

Euler's Criterion

Let p be a prime number. r is a quadratic residue mod p if and only if

$r^{\frac{p - 1}{2}} \equiv {1\mspace{14mu}{mod}\mspace{14mu} p}$

Modular Square Roots (p=3 mod 4)

Let p be a prime number such that p≡3 mod 4. Then for any integer rsatisfying Euler's criterion, if a is an integer such that

a ² ≡r mod p

Then there exists a solution for a of the form

$a \equiv {{\pm r^{\frac{p + 1}{4}}}\mspace{14mu}{mod}\mspace{14mu} p}$

Chinese Remainder Theorem

Given pairwise coprime positive integers n₁, n₂, . . . , n_(k) andarbitrary integers a₁, a₂, . . . , a_(k), the system of simultaneouscongruences

x ≡ a₁  mod  n₁ x ≡ a₂  mod  n₂ ⋮ x ≡ a_(k)  mod  n_(k)

has a unique solution modulo N=n₁n₂ . . . n_(k). As a special case ofthe Chinese Remainder Theorem, it can be shown that

x≡r mod n ₁ and x≡r mod n ₂

if and only if

x≡r mod n ₁ ·n ₂

The Rabin Digital signature Algorithm

The Rabin digital signature algorithm can be described as follows:

For any message m let H be a collision resistant hashing algorithm withk output bits. To generate the keys, choose prime numbers p and q, eachwith bit-length approximately k/2 such that p≡3 mod 4, q≡3 mod 4 andcompute the product n=p·q. The private keys are (p, q) and the publickey is n=p·q.

To sign the message, m, the signer chooses a padding U such that H(m∥U)satisfies

${H\left( {m{}U} \right)}^{\frac{p - 1}{2}} \equiv {1\mspace{14mu}{mod}\mspace{14mu} p}$${H\left( {m{}U} \right)}^{\frac{q - 1}{2}} \equiv {1\mspace{14mu}{mod}\mspace{14mu} q}$

The signature, S, is computed using the formula

$S \equiv {\left\lbrack {{\left( {{p^{q - 2} \cdot {H\left( {m{}U} \right)}^{\frac{q + 1}{4}}}\mspace{14mu}{mod}\mspace{14mu} q} \right) \cdot p} + {\left( {{q^{p - 2} \cdot {H\left( {m{}U} \right)}^{\frac{p + 1}{4}}}\mspace{14mu}{mod}\mspace{11mu} p} \right) \cdot q}} \right\rbrack\mspace{14mu}{mod}\mspace{14mu}{n.}}$

The signature for the message m is the pair (S, U). Verification can besimply done by checking that, for a given m, U and S

H(m∥U)≡S ² mod n  (Equation 1).

This is true if and only if there exists an integer λ in the range 0, .. . , n−1 such that

H(m∥U)+λ·n=S ²  (Equation 2).

The factor λ may be safely included in the signature, to provide thecombination (S, λ, U).

The advantageous features of the Rabin signature scheme are as follows:

-   -   a) Signature generation is computationally expensive, whereas        verification of the signature is computationally easy.    -   b) The security of the signature relies only on the hardness of        integer factorisation. As a result, Rabin signatures are        existentially unforgeable (unlike RSA).    -   c) The hash function values H(m∥U) must be of a similar        magnitude to the public key n.

Verification in script is straightforward as it only requires squaring agiven signature, performing a modular reduction and then checking thatthe result is equal to H(m∥U).

Rabin Signature Proof

Let p, q be coprime and n=p·q. By the Chinese Remainder Theorem it canbe shown that

S ² ≡H(m∥U)mod n

If and only if

S ² ≡H(m∥U)mod p

S ² ≡H(m∥U)mod q

It can be shown that

S ² ≡H(m∥U)mod q

Using

$\begin{matrix}{S \equiv} & {\left( {{\left( {p^{q - 2}{H\left( {m{}U} \right)}^{\frac{q + 1}{4}}\mspace{14mu}{mod}\mspace{14mu} q} \right) \cdot p} +} \right.} \\ & {\left. {\left( {q^{p - 2}{H\left( {m{}U} \right)}^{\frac{p + 1}{4}}\mspace{14mu}{mod}\mspace{14mu} p} \right) \cdot q} \right)\mspace{14mu}{mod}\mspace{14mu} q} \\{\equiv} & {\left( {\left( {p^{q - 2}{H\left( {m{}U} \right)}^{\frac{q + 1}{4}}\mspace{14mu}{mod}\mspace{14mu} q} \right)p} \right)\mspace{14mu}{mod}\mspace{14mu} q} \\{\equiv} & {p^{q - 2}{{H\left( {m{}U} \right)}^{\frac{q + 1}{4}} \cdot p}\mspace{14mu}{mod}\mspace{14mu} q} \\{\equiv} & {\left( {p^{q - 1}\mspace{14mu}{mod}\mspace{14mu} q} \right){H\left( {m{}U} \right)}^{\frac{q + 1}{4}}\mspace{14mu}{mod}\mspace{14mu} q} \\{\equiv} & {{H\left( {m{}U} \right)}^{\frac{q + 1}{4}}\mspace{14mu}{mod}\mspace{14mu} q}\end{matrix}$

Therefore

$S^{2} \equiv {H\left( {m{}U} \right)}^{\frac{q + 1}{2}} \equiv {{H\left( {m{}U} \right)}^{\frac{q - 1}{2}} \cdot {H\left( {m{}U} \right)}} \equiv {{H\left( {m{}U} \right)}\mspace{14mu}{mod}\mspace{14mu} q}$

Where it has been assumed that H(m∥U) satisfies Euler's criterion. By asimilar calculation one can also show that

S ² ≡H(m∥U)mod p

Rabin Signatures in Bitcoin

Signature Verification in Script

A small number of arithmetic and stack manipulation opcodes are requiredto verify a Rabin signature. Consider a redeem script of the form

-   OP_DUP OP_HASH160<H₁₆₀(n)> OP_EQUALVERIFY OP_MUL OP_SWAP OP_2    OP_ROLL OP_CAT FUNC_HASH3072 OP_ADD OP_SWAP OP_DUP OP_MUL OP_EQUAL    where n is the public key of the signer. This will evaluate to TRUE    if and only if is provided with the input    -   <S><U><m><λ><n>        where m is an arbitrary message, and (S, λ, U) is a valid Rabin        signature. Alternatively, if the Rabin signature is checked        using equation 1 above the redeem script is given by-   OP_DUP OP_HASH160<H₁₆₀(n)> OP_DUP OP_TOALTSTACK OP_SWAP <roll index>    OP_ROLL OP_CAT FUNC_HASH3072 OP_SWAP OP_MOD OP_SWAP OP_DUP OP_MUL    OP_FROMALTSTACK OP_MOD OP_EQUAL

In this case the script will evaluate to TRUE if and only if is providedwith the input

-   -   <S><U><m><n>

In both redeem scripts, use has been made of the 3072-bit hashprojection function ‘FUNC_HASH3072’. For a given message/paddingconcatenation the FUNC_HASH3072 hash projection is generated using thescript

-   OP_SHA256 {OP_2 OP_SPLIT OP_SWAP OP_SHA256 OP_SWAP} (x11)-   OP_SHA256 OP_SWAP OP_SHA256 {OP_CAT}(x11)

Compression of Data

Internet data consists of JavaScript and common file types such as textfiles (SML, HTML, etc.), video files (MPEG, M-JPEG etc.), image files(GIF, JPEG etc.) and audio files (AU, WAV, etc.), for example asdescribed in greater detail athttps://www.doc.ic.ac.uk/˜nd/surprise_97/journal/vol1/mmp/#text. Usingthe above data insertion techniques, these different data types can alsobe embedded on the blockchain.

Larger file sizes can be compressed using one of several existing codingschemes before embedding it on the blockchain. Lossless data compressionalgorithms such as Run-length and Huffman encoding can be used inseveral applications, including ZIP files, executable programs, textdocuments and source code.

Many different algorithms exist depending on the specific input data.Apple Lossless and Adaptive Transform Acoustic Coding can be used tocompress audio files, PNG and TIFF for the compression of Graphicsfiles, while movie files can be compressed using one of many losslessvideo codecs. Any compression of the data content can be indicated usinga flag within the attributes. For example, the flag for the LZW losslesscoding scheme in the attributes would be <LZW>.

Encryption and Paid Decryption

Encryption of Data

The owner of the content may choose to protect the content beforeembedding it on the Blockchain. This ensures that the content cannot beviewed without acquiring the necessary permissions.

There are many well-established techniques for the encryption of data(either plaintext or other data types). These can be categorised asasymmetric encryption or symmetric encryption.

Elliptic Curve Cryptography (ECC) is asymmetric as it relies on apublic-private key pair. It is one of the most secure cryptosystems andis typically used in cryptocurrencies such as bitcoin. For ECCcryptography the Koblitz algorithm can be used to encrypt data.

In symmetric schemes a single key is used to both encrypt and decryptthe data. The Advanced Encryption Standard (AES) algorithm is consideredone of the most secure symmetric algorithms that is seeded by such asecret, for example as described in greater detail in C. Paar and J.Pelzl, Chapter 4 in “Understanding Cryptography,” Springer-Verlag BerlinHeidelberg 2^(nd) Ed., 2010, pp. 87-118.

When encrypting data stored on a blockchain there are advantages inusing the same cryptosystems as the underlying blockchain. In bitcointhis is the secp256k1 conventions for ECC key pairs in asymmetriccryptography, and the SHA-256 hash function in symmetric cryptography.These advantages are:

-   -   The security level of the encryption is the same as the        underlying system in which the data is stored on.    -   The software architecture needed for storing encrypted data will        have a smaller codebase.    -   The management of keys in a wallet can be used both for        transactions and encryption/decryption.    -   It is more efficient as the same keys can be used both for        encryption and payment in the cryptocurrency, so fewer keys are        required. This also reduces storage space.    -   Fewer communication channels may be needed to exchange/purchase        the ability to decrypt data.    -   There is increased security as keys used for encryption and        transactions are the same data structure and so targeted attacks        for a specific type of key are mitigated.    -   Keys can be purchased using the underlying cryptocurrency.

For illustrative purposes, how the Koblitz algorithm can be used toencrypt data using ECC is described.

Koblitz Algorithm

Given a ECC key pair P₁=S₁·G the Koblitz algorithm allows anyone toencrypt a message using the public key P₁ such that only someone whoknows the corresponding private key S₁ may decrypt the message.

Suppose it is desired to encrypt the plaintext message ‘hello world’using the Koblitz method. This is done character-by-character. The firstcharacter ‘h’ is encrypted and decrypted as follows.

-   -   1. The character ‘h’ is mapped to a point on the secp256k1        curve. This is achieved by using the ASCII conventions to map a        plaintext character to an 8-bit number. A point on the curve is        then calculated by multiplying the base point G by this number.        In the present example ‘h’ is mapped to 104 in ASCII, and the        elliptic curve point is given by P_(m)=104·G.    -   2. The point P_(m) is then encrypted using the public key P₁.        This is achieved by choosing a random ephemeral key k₀ and        calculating the pair of points C_(m)={k₀·G,Q} where        Q:=P_(m)+k₀·P₁, which may then be broadcast.    -   3. The owner of the private key S₁ may decrypt the original        point by calculating P_(m)=Q−S₁·k₀·G. They may then recover the        original ASCII number by trial-and-error or by means of a look        up table to establish which number x corresponds to P_(m)=x·G.

Using the Blockchain to Purchase Permissions

Storing data on a blockchain has the obvious advantage that a paymentmechanism is built into the system. Payments can be used to purchase

-   -   Decryption data in order to view/use    -   Permission to insert data at a particular address

In both cases the buyer is using a cryptocurrency, for example Bitcoin,to purchase a secret that grants them permission to do something. Thissecret may be either a hash preimage or a private key.

An efficient and secure way to make such a purchase is to use an atomicswap. This keeps secure communication channels to a minimum and ensuresthat either the seller gets paid and the secret is revealed to thebuyer, or neither event occurs.

Besides payments in cryptocurrencies, it can also be convenient topurchase a permission using an access token. This is a secret value(typically a hash preimage) that the buyer owns that they can use inorder to make a purchase. Such tokens may be bought in bulk by the buyerahead of time, and then activated at the time they would actually liketo use the permission.

How atomic swaps are executed will now be described with reference toFIGS. 4 and 5.

Atomic Swaps Using Hash Puzzles or Private Key Puzzles

Suppose Alice is the owner of the secret. This secret may be either ahash preimage of a known hash digest, or the private key of a knownpublic key. Suppose Bob wishes to use Bitcoin to buy this secret fromAlice. A mechanism known as an atomic swap is described that enablesthis transaction to occur. It is atomic in the sense that either Alicegets paid Bitcoin and the secret is revealed to Bob, or neither eventoccurs.

The method is as follows:

Alice owns a private key S_(A) of a public/private key pairP_(A)=S_(A)·G and Bob owns a private key S_(B) of a public/private keypair P_(B)=S_(B)·G.

Alice owns a secret which is either the preimage X of a known hashdigest H(X), or the private key S₁ of a known public key P₁=S₁·G.

They agree on a price in Bitcoin for Alice to sell the secret to Bob.

Prior to these, Bob must set up a transaction to send Alice theephemeral key k₀ off-block so that she can calculate r₀, a component ofa digital signature.

Referring now to FIG. 4,

-   -   1. Bob transfers Bitcoin to Alice that are locked with the        following redeem script        R (written schematically):    -   For a hash preimage:

R=[Hash Puzzle H(X)][CheckSig P _(A)]

This forces the preimage X to be exposed in the input of the redeemscript.

-   -   For a private key:

R=[Private Key Puzzle P ₁ ,r ₀][CheckSig P _(A)]

This forces the private key S₁ to be able to be calculated from theinput to the redeem script. In this case Bob and Alice must agree on anephemeral key k₀ that is used to construct r₀, where (r₀, R_(y))=k₀·G.

-   -   2. Since Alice knows her secret (either X or S₁) she can spend        her funds on the Bitcoin blockchain by means of the transaction        shown in FIG. 5. This allows Bob to determine her secret.

As an optional security feature, Alice and Bob may use their public keysP_(A), P_(B) to establish a shared secret S known only to both parties.This could be achieved in a manner outlined in International PatentPublication no. WO 2017/145016. In this case S may be added to thepreimage X in the hash puzzle in order for X not to be revealed publiclyon the blockchain. Similarly, in the private key puzzle S may be used asthe ephemeral key k₀ to ensure that only Alice or Bob is able tocalculate the private key.

A time-locked refund can be introduced to the procedure to prevent Bob'sfunds being locked by Alice, should Alice decide not to spend her funds.

Purchase Using Tokens

Suppose that the same situation exists as described above, but insteadpaying in cryptocurrency for Alice's secret at its point of use Bobwould like to redeem an access token—that he has bought ahead of time—inexchange for the secret.

The procedure that Alice and Bob must follow is similar to the casedescribed in the previous section, but instead uses a sequence ofsimilar atomic swaps. There are two phases of the process; tokenissuance and token redemption.

Phase 1: Token Issuance

The token issuance phase is effectively a one-time purchase of tokens byBob. For example, we will consider the scenario where Alice has 10distinct secrets X₁, X₂, . . . , X₁₀ and Bob wishes to make a singlepurchase for 10 tokens T₁, T₂, . . . , T₁₀ which each grant him accessto a respective secret.

First Bob generates a set of 10 tokens from a secret seed value Y knownonly to him. These tokens are created by sequential hashing of the seedto form a hash chain, where each token is calculated as

T _(i) =H ^(10-i)(Y) for i∈{1,2, . . . ,10}.

Alice and Bob now have 10 secret values each, which can be revealed inhash puzzles for example, for the redemption of tokens. In order toissue these tokens however, they must also generate a secretinitialising value I_(Alice) and I_(Bob) respectively. These are givenas

I _(Alice) =k, k∈

₂₅₆,

I _(Bob) =H ¹⁰(Y).

It should be noted that Alice's initialiser is simply a random integerwith no specific meaning, but Bob's initialiser should be the hash ofhis first token T₁=H⁹(Y). Extending the chain of tokens to theinitialiser in this way allows the token issuance to also define thetoken to be used later for successive redemptions. In total the secretvalues kept by each participant are shown in FIG. 6.

Now Alice and Bob can agree to a price of 10 cryptocurrency units forthe purchase of 10 tokens. The purchase of these tokens can happen in anumber of ways, this is illustrated here using an atomic swap. Theatomic swap is initiated by Alice and Bob broadcasting the transactionsshown in FIGS. 7 and 8 respectively, in both of which the outputsrequire the solution to two hash puzzles and a valid signature.

Once both transactions appear in the blockchain Alice and Bob can sharetheir share initialiser values I_(Alice) and I_(Bob) and complete theatomic swap for token issuance. As a result of this atomic swap Alicereceives payment for the purchase of 10 tokens and both initialisersecrets are revealed. It should be noted that only Bob's secretI_(Bob)=H¹⁰(Y) is meaningful here because it will define the first hashpuzzle to be solved [Hash Puzzle (T₁)], whose solution is the preimageH⁹(Y) of the initialiser H¹⁰(Y).

Phase 2: Token Redemption

At some point in the future Bob wants to redeem his first token T₁=H⁹(Y)and receive his first secret X₁, but it will be recalled that he hasalready paid for this secret by purchasing a valid token. The process ofredeeming a token will take the form of another atomic swap, where thesolutions to the locking hash puzzles are a token T_(i) andcorresponding secret X_(i).

To redeem his token, Bob should broadcast the transaction shown in FIG.9, whose output is locked with the two hash puzzles. When Alice seesthis transaction she broadcasts her own similar transaction as shown inFIG. 10, whose output is locked with the same two hash puzzles. The twoparticipants can now exchange their secrets T₁ and X₁ and unlock theoutputs to these transactions. Both parties can now redeem the nominalfee x by providing the correct unlocking script that also exposes bothsecrets. The transactions with these unlocking scripts are shown inFIGS. 11 and 12.

The completion of this atomic swap for redeeming a token reveals Alice'sfirst secret X₁ to Bob, reveals Bob's first token T₁ to Alice and has anet-zero exchange of cryptocurrency funds, given that the amount x issuitably large to encourage both parties to spend the locked outputs.Crucially, this also establishes that the next token Bob can use must bethe solution T₂ to the hash puzzle [Hash Puzzle H(T₂)], where the targethash H(T₂)=T₁ has just been revealed to Alice. This process can berepeated recursively until Bob has used his final token T₁₀=Y.

Naming and Addressing

Node and Edge Structure

It has been explained above how data can be inserted into the blockchainby providing it within transactions. We now present a protocol forstructuring these transactions in logical way that allows for addressingof nodes, permissions, and content version control. The structure ofthis distributed peer metanet is analogous to the existing internet.

It should be noted that this is a “tier-2” protocol that does not modifythe protocol or consensus rules of the underlying blockchain.

The aim of the structure described here is to

-   -   (I) Associate related content in different transactions to        enable searching, identification and access to the data    -   (ii) Allow identification of content using human-readable        keyword searches, to improve speed, accuracy and efficiency of        searching    -   (iii) Build and emulate server-like structures within a        blockchain

Our approach is to structure data associated with the Metanet as adirected graph. The nodes and edges of this graph correspond to:

-   -   Node—A transaction associated with the Metanet protocol. A node        stores content. (The terms “content” and “data” may be used        interchangeably within this document).    -   A node is created by including an OP_RETURN that is immediately        followed by <Metanet Flag>. Each node is assigned a public key        P_(node). The combination of public key and transaction ID        uniquely specify the index of the node ID_(node):        =H(P_(node)∥TxID_(node)).    -   The hash function used should be consistent with the underlying        blockchain protocol that the invention is to be used with e.g.        SHA-256 or RIPEMD-160 for Bitcoin.    -   Edge—An association of a child node with a parent node.    -   An edge is created when a signature Sig P_(parent) appears in        the input of a Metanet transaction, and therefore only a parent        can give permission to create an edge. All nodes may have at        most one parent, and a parent node may have an arbitrary number        of children. In the language of graph theory the indegree of        each node is at most 1, and the outdegree of each node is        arbitrary.

It should be noted that an edge is an aspect of the Metanet protocol andis not itself a transaction associated with the underlying blockchain.

A valid Metanet node (with parent) is given by a transaction of thefollowing form:

TxID_(node) Input Output <Sig P_(parent)> <P_(parent)> OP_RETURN<Metanet Flag> <P_(node)> <TxID_(parent)>

This transaction contains all the information needed to specify theindex of the node and its parent

ID_(node) =H(P _(node) ∥TxID_(node)), ID_(parent) =H(P _(parent)∥TxID_(parent)).

Moreover, since the signature of the parent node is required, only aparent can create an edge to a child. If the <TxID_(parent)> field isnot present, or it does not point to a valid Metanet transaction, thenthe node is an orphan. It has no higher-level node by which it can bereached.

Additional attributes may be added to each node. These may includeflags, names and keywords. These are discussed later in the thisdocument.

As shown, the index of a node (transaction) can be broken down into

-   -   a) Public Key P_(node), which we interpret as the address of the        node    -   b) Transaction ID TxID_(node), which we interpret as the version        of the node

Two advantageous features arise from this structuring:

-   -   1. Version control—If there are two nodes with the same public        key, then we interpret the node with transaction ID with        greatest proof of work as the latest version of that node. If        the nodes are in different blocks, then this can be checked with        the block height. For transactions in the same block, this is        determined by the Topological Transaction Ordering Rule (TTOR).    -   2. Permissioning—A child of a node can only be created if the        owner of the public key P_(node) signs the transaction input in        the creation of a child node. Therefore P_(node) not only        represents the address of a node but also the permission to        create a child node. This is intentionally analogous to a        standard bitcoin transaction—a public key in not only an address        but also the permission associated with that address.    -   Note that since the signature of the parent node appears in a        UXTO unlocking script it is validated through the standard miner        validation process at the point when the transaction is accepted        to the network. This means that the permission to create a child        node is validated by the bitcoin network itself.

It is worth noting that standard Internet Protocol (IP) addresses areunique only within a network at a certain point in time. On the otherhand, the index of a node in the Metanet is unique for all time andthere is no notion of separate networks, which allows data to bepermanently anchored to a single object ID_(node).

The node and edge structure allow us to visualise the Metanet as agraph, as shown in FIG. 13.

Domains, Naming and Locating Content within the Metanet

The hierarchy of the Metanet graph allows rich domain-like structure toemerge. We interpret an orphan node as a top-level domain (TLD), a childof an orphan node as a sub-domain, a grandchild as a sub-sub-domainetc., and a childless node as an end-point. See FIG. 13.

The domain name is interpreted as ID_(node). Each top-level domain inthe Metanet may be thought of as a tree with the root being the orphannode and the leaves being the childless nodes. The Metanet itself is aglobal collection of trees which form a graph.

The Metanet protocol does not stipulate that any node contains contentdata, but leaf (childless) nodes represent the end of a directed path onthe data tree, and thus will be used generally to store content data.However, content may be stored at any node in the tree.Protocol-specific flags, included in nodes as attributes, may be used tospecify the role of nodes in a data tree (disk space, folders, files orpermissioning changes).

Recall that the internet uses the Domain Name System (DNS) to associatehuman-readable names to Internet Protocol (IP) addresses. The DNS is ina sense decentralised, although in practice it is controlled by a smallnumber of key players, such as governments and large corporations.Depending on your DNS provider the same name may take you to differentaddresses. This issue is inherent when mapping short human-readablenames to computer generated numbers.

We assume that an equivalent distributed system exists that maps ahuman-readable top-level domain name to the decentralised indexID_(root) of a root node. In other words, there exists a 1-1 function κthat maps human-readable names to Metanet root node indexes, for example

κ(‘bobsblog’)=ID_(bobsblog) (=H(P _(bobsblog) ∥TxID_(bobsblog))).

The input to the left-hand-side is human-readable word, whereas theoutput on the right-hand-side is a hash digest, which will typically bea 256-bit data structure. Note that P_(bobsblog) and TxID_(bobsblog) arealso not human readable in general. In the standard IP protocol thiswould be a map from www.bobsblog.com to the IP address of thecorresponding domain within the network.

The map κ should be interpreted as a measure to ensurebackwards-compatibility of the Metanet with the internet in replicatingthe human-readability of DNS-issued domain names, but the naming andaddressing scheme that provides the structure of the Metanet is notexplicitly dependent on this map.

Possible existing forms of the mapping function κ include the DNSLinksystem employed by Interplanetary File System (IPFS) or the OpenNICservice (https://www.openic.org). This mapping can be stored in anexisting TXT record as part of the DNS. This is similar to a DNSLink inthe IPFS—see https://docs.ipfs.io/guides/concepts/dnslink/. However, ingeneral these sacrifice some element of decentralisation in order toprovide a map that is 1-1—seehttps://hackernoon.com/ten-terrible-attempts-to-make-the-inter-planetary-file-systern-human-friendly-e4e95df0c6fa

Vanity Addresses

The public key used as the address of a Metanet node is not ahuman-readable object. This can make searching, referencing andinputting activities error prone and slow for human users. However, itis possible to create human-recognisable public key addresses—vanityaddresses P_(vanity)—which include a plaintext prefix that can beinterpreted directly by a user. Vanity addresses are known in the priorart.

The difficulty in creating such an address depends on the characterlength of the desired prefix. This means that human-recognisable vanityaddresses may be used as node addresses that rely only on the effort ofthe owner to create rather than on central issuance. For a given prefixthere exist many distinct vanity addresses, due to the charactersremaining in the suffix, and hence many node addresses can share acommon prefix whilst still retaining uniqueness.

An example of a vanity address with a desirable prefix is

-   P_(bobsblog):bobsblogHtKNngkdXEeobR76b53LETtpyT    -   Prefix: bobsblog    -   Suffix: HtKNngkdXEeobR76b53LETtpyT

The vanity address above may be used to sense check the map from thename ‘bobsblog’ to the node index ID_(bobsblog) and to aid thesearchability of Metanet nodes by address. Note that the prefix is notunique here but the entire address itself is a unique entity.

The combination of a chosen address P_(vanity) with a TxID that togetherform ID_(node) is also beneficial as it means there is no central issuerof domain names (TxIDs are generated by decentralised proof-of-work) andthe names are recoverable from the blockchain itself. Advantageously,there are no longer the points of failure that exist within the internetDNS.

Since Metanet domains already provide a permissions system (the publickey) there is no need to issue a certificate to prove ownership. The useof a blockchain for this purpose has already been explored in namecoin(https://namecoin/org/) for example. In accordance with the presentinvention, however, there is no need to use a separate blockchain forthis function as everything is achieved within one blockchain.

This significantly reduces the amount of resources (hardware, processingresources and energy) required by the invention in comparison to theprior art. It also provides an entirely different architecture in termsof apparatus and arrangement of system components.

An advantage of this naming system is that a user is able to identify atop-level domain in the Metanet by a memorable word (for example acompany name) rather than a hash digest. This also makes searching forthe domain faster as it is quicker to search for a keyword rather than ahash digest. It also reduces input errors, thus providing an improvedsearching tool for blockchain-stored data.

Given that we have a map from a domain name to a node index we can buildup a resource locator similar to that of a Uniform Resource Locator(URL) for the internet. We will call this a Metanet URL (MURL), andtakes the form

MURL=‘mnp:’+‘//domain name’+‘/path’+‘/file’.

Each of the components of a URL—protocol, domain name, path andfile—have been mapped to the structure of a MURL, making the object moreuser-intuitive and enabling it to be integrated with the existingstructure of the internet.

This assumes that each node has a name associated with its public key(address) that is unique at the level within the domain tree. This nameis always the right-most component of the MURL for a given node. If twonodes at the same level in the tree have the same name then they willhave the same public key and so the latest version is taken.

The following table gives an analogy between the Metanet protocol andthe Internet Protocol:

TABLE Summary of the analogies between the Internet and MetanetProtocols. Internet Metanet Website/file Node Owner Public Key P_(node)IP Address (non-unique) Node index (unique) ID_(node) = H(P_(node)||TxID_(node)) Domain structure Node tree structure Domain NameSystem Map from root node name to node index URL MURLhttp://www.bobsblog.com/path/file mnp://bobsblog/path/file

Searching the Metanet

We have defined an illustrative embodiment the Metanet graph structuresuch that each node has a unique index and may have a name attributed toit. This allows for content to be located using a MURL. In order to alsoenable quick search functionality, we allow for additional keywords tobe attributed to a node.

The fixed attributes of a node are the index and index of parent node,and the optional attributes are the name and keywords.

Node attributes { index: H(P_(node)∥TxID_(node)); index of parent:H(P_(parent)∥TxID_(parent)); (NULL if orphan) name: ‘bobsblog’; kwd1:‘travel’; kwd2: ‘barbados’;  .  .  . }

In one example, a practical method for searching the Metanet may be tofirst use a block explorer to trawl through the blockchain and identifyall transactions with the Metanet flag, check that they are validMetanet nodes, and if so record their indexes and keyword in a databaseor other storage resource. This database can then be used to efficientlysearch for nodes with desired keywords. Once the index of the node(s)with the desired keywords is found its content can be retrieved from theblock explorer and viewed.

By way of example, consider the P₁ branch of FIG. 14, where the nodescorresponding to public keys P₀, P₁ and P_(1,1) represent a home page,topic page and sub-topic page respectively. These nodes are given thenames ‘bobsblog’, ‘summer’ and ‘caribbean’, and their attributes areshown below

Home page node P₀ MURL: mnp://bobsblog { index: H(P₀∥TxID₀); index ofparent: NULL name: ‘bobsblog’; kwd1: ‘travel’; kwd2: ‘barbados’;  .  . . } Topic page node P₁ MURL: mnp://bobsblog/summer { index:H(P₁∥TxID₁); index of parent: H(P₀∥TxID₀); name: ‘summer’; kwd1:‘travel’; kwd2: ‘barbados’;  .  .  . } Sub-topic page node P_(1,1) MURL:mnp://bobsblog/summer/caribbean { index: H(P_(1,1)∥TxID_(1,1)); index ofparent: H(P₁∥TxID₁); name: ‘caribbean’; kwd1: ‘travel’; kwd2:‘barbados’;  .  .  . }

In this example, the leaf nodes P_(1,1,1) P_(1,1,2) and P_(1,1,3) aregiven the names ‘beaches’, ‘nightlife’ and ‘food’ respectively and areused to store separate blog posts. The full domain structure is shown onthe diagram overleaf, including the MURL search path pertaining to eachnode in the tree.

We note that the Metanet can also incorporate a content addressablenetwork (CAN) by storing a hash of the content stored by a nodetransaction as an additional attribute. This means Metanet nodes mayalso be indexed and searched for by content hash.

The naming and addressing methods described above provide numeroustechnical advantages over the prior art, including:

-   -   1. Public key addresses—The system uses the same public-private        key pairs as the blockchain to assign node addresses. This means        that the same set of keys are used for both management of        cryptocurrency funds and permissioning of content data. This        provides an efficient and secure solution.    -   2. Decentralised domains—The issuance of domain names is fully        decentralised through the inclusion of the TxID_(node), which        can only be generated by proof of work. The domain names can        also incorporate human-recognisable public keys P_(vanity)        (vanity addresses) which enable the fair distribution of desired        domain public keys. Again, this solution provides enhanced        efficiency and security.    -   3. Graph structure—The naming and addressing architecture        specifies a graph that can be constructed from the subset of        blockchain data comprising Metanet nodes. This design maps the        complexity of the internet to the blockchain using an ordered        structure such that it fully replicates its functionality and        scalability whilst remaining secure.

Browser-Wallet Application

Recall that in the Metanet protocol all data lives directly on theblockchain itself. In this section we present embodiments of anillustrative computer application, which we will refer to herein forconvenience only as a “browser-wallet”, that can efficiently access,display and interact with Metanet data stored on the blockchain.

We will begin with a discussion of the core components andfunctionalities of how the browser-wallet interfaces with thedistributed peer internet, before providing a more detailed descriptionin the remainder of this section.

Overview

Components

The browser-wallet is an application intended to allow an end-user tointeract with the Metanet infrastructure on the blockchain. Thisapplication should allow explorative searches of the Metanet graph forspecific content embedded in trees. Additionally, the browser-walletwill handle retrieval, decryption, recombination and caching (optional)of content.

The browser-wallet application will combine these elements withcryptocurrency payment mechanisms by supporting a native (or external)wallet. The browser-wallet will comprise the following core elements,combined into a single computer application.

-   -   Blockchain search engine—Support for a third-party search engine        to query Metanet nodes by a variety of indexes including        ID_(node), node name, keywords, block height and TxID.    -   Display window—Software that unpacks content returned to the        browser by a full-copy blockchain peer. This covers decryption,        recombination, caching and redemption of access tokens.    -   Cryptocurrency wallet—Dedicated key-management for currency of        the blockchain. Can be native to the application or authorised        to communicate and synchronise with external wallet (software or        hardware). Able to write standard blockchain transactions as        well as new Metanet node transactions. Can mediate on-chain        purchase of access keys and access tokens.    -   Hierarchical, deterministic key management is leveraged for both        cryptocurrency public keys and Metanet node addresses.    -   Access key/token wallet—Dedicated key-management for purchased        access keys or tokens. Can receive purchased keys or tokens        using cryptocurrency wallet but has no permissions over them.        They may be hidden to the user to allow later expiry. This may        be achieved through the use of a trusted execution environment.        Timed-access can be secured by synchronising with the blockchain        and querying current block height.

Functionality

The specification for the Metanet browser-wallet ensures the followingfunctionalities of the application.

-   -   1. Hierarchical key-management—The keys used for controlling        funds and managing Metanet trees (graphs) utilise the same        hierarchical deterministic key infrastructure, reducing the        burden on users to maintain key records for their Metanet        content.    -   2. Pointing to an external cryptocurrency wallet—Ability to        authorise and synchronise with an external (non-native to        application) wallet allows for additional security by removing        the browser-wallet as a point of failure. The application can        write blockchain transactions and require the signature of an        external wallet that houses keys, delegating this responsibility        to separate software or hardware.    -   3. Searching of Metanet content—The browser-wallet can support        and query a third-party search engine whose functions may        comprise crawling, indexing, servicing and ranking Metanet node        transaction data in a global database. A database of OP_RETURN        transactions containing the Metanet protocol flag may be        constructed. See BitDB 2.0—https://bitdb.network./.        -   The search engine can serve the browser-wallet with a node            index, which allows data to be found.    -   4. Reading and writing data to blockchain—In addition to using        search engines and full-nodes to serve the browser with content,        the support for a cryptocurrency wallet also allows for content        to be written into the Metanet directly from the browser-wallet.    -   5. Decompression and decryption of data—The browser-wallet        handles decryption keys and can perform decompression on Metanet        content in-situ.    -   6. Caching node identities (ID_(node))—Unique node identities        can be cached locally for more efficient lookup and querying.    -   7. Bypassing web-servers—Given a node index, the browser-wallet        can query any full-copy member of the peer-to-peer (P2P)        blockchain network for the content located at a node. Because        the Metanet lives on-chain, any full-copy peer must have a local        copy of the node and its content.        -   This means that the user's browser-wallet need only query a            single peer, which can be done directly and without the need            for an intermediary web-server.        -   FIG. 15 shows the schematic for the browser-wallet and how            its core functions are split across different components of            the application.

Blockchain Search Engine

Search Engines—Existing Technologies

Search engines (SEs) as known in the prior art rely on powerful webcrawlers to locate, index and rank web content according to the userqueries. (The same underlying principles can be extended to athird-party Blockchain SE that crawls the Metanet).

SEs identify relevant HTML metatags and content through a search of thekeywords in the query. The results of the crawl are subsequently indexedwhere any embedded images/videos/media files are analysed andcatalogued. The most relevant results from the index are then rankedprogrammatically, taking into consideration the user's location,language and device.

A typical SE should have the following functionality:

-   -   1. Crawling—Identify internet data and crawl through the        relevant metadata, such as domain names, linked pages and        related keywords. New internet content is discovered through        existing content and also crawled for any relevant information.    -   2. Indexing—Content data are analysed and catalogued. This        information is stored in the database.    -   3. Servicing and ranking—Content indexes are ranked in order of        relevance to the users' queries.

Block Explorers

The closest blockchain analogue to an internet search engine (SE) is ablockchain explorer, sometimes referred to as a ‘block explorer’ or‘blockchain browser’. Blockchain explorers are web applications whichenable user-friendly queries of a blockchain, at a high level, andfunction similarly to web browsers but are connected to a blockchainrather than the internet. Seehttps://en.bitcoin.it/wiki/Block_chain_browser.

In most cases, these explorers allow blocks (indexed by hash of theblock header), transactions (indexed by TxID), addresses and unspenttransaction outputs (UTXOs) to be taken as inputs and searched for. Manyexplorers also offer their own application programming interfaces (APIs)for retrieving raw transaction and block data. Seehttps://blockexplorer.com/api-ref.

Block explorers, while varying in their capabilities, are generallyuseful for cataloguing transactions and displaying their basicinformation—such as transacted currency values, confirmations andhistories of coins and addresses—in a form that is easy for users todigest. Many explorers, such as Bitcoin.comhttps://explorer.bitcoin.com/bch and Blockchain.comhttps://www.blockchain.com/explorer also allow the individual input andlocking scripts for transactions to be viewed, although there areinconsistencies between how these and more advanced sites likeBlockchain https://blockchair.com/ choose to provide this information.

Recently there have been many extensions of basic blockchain explorersused to run web applications based on blockchain data. Theseapplications, such as Memo.cash https://memo.cash/protocol and Matterhttps://www.mttr.app/home act like block explorers that catalogue andorganise blockchain transactions that contain specific protocolidentifiers, as well as displaying data encoded within those particulartransactions.

However, there are two important issues with using blockchain explorersthat are addressed by embodiments of the present invention:

-   -   1. Universality—There is currently no industry-wide standard for        browsing content data that is stored in transactions. Content        data refers to any data that does not pertain to the protocol        used for creating and securing the underlying blockchain.    -   2. Keyword searching—Content data stored in transactions needs        to be retrievable by human-readable keywords. This is not        generally a function of current block explorers as they are used        to query the protocol-based properties of transactions, such as        block height, TxID and addresses rather than taking keywords as        search inputs. (However, some e.g. Blockchain can search for        words if they are directly included in the script of the        transaction).

Importantly, the powerful naming and addressing structure of the presentinvention, as discussed above, facilitates and enables the constructionof a more sophisticated blockchain explorer than known in the art.

Proposed Metanet Search Engine

The browser-wallet application communicates with a third-party searchengine for discovery of node identities (ID_(node)). It is envisagedthat such a third-party may provide a powerful and versatile servicethat replicates the capabilities of existing internet search engines.

A Metanet search engine third-party maintains a database of all Metanettransactions mined into the blockchain identifiable by the Metanetprotocol flag. This database can catalogue all Metanet nodes by a rangeindexes including ID_(node), node names, key words, TxID and blockheight.

There already exist services, such as Bit DB https://bitdb.network/,which continuously synchronise with the blockchain and maintaintransaction data in a standard database format. The browser-walletoffloads the responsibilities of crawling, indexing, servicing andranking Metanet transactions to such a third-party and makes aconnection to their services when locating content stored on the Metanetgraph.

Efficiency savings may be made by having a database that is dedicated toMetanet data only. Unlike Bit DB this would not store the dataassociated with all transaction, only those containing the Metanet flag.Certain databases, such as non-relational databases like MongoDB, may bemore efficient at storing the graph structure of the Metanet. This wouldallow for faster querying, lower storage space, and more efficientlyassociate related content within Metanet domains.

FIG. 16 shows how the browser-wallet interacts with a third-party searchengine when a user searches for content within the Metanetinfrastructure. Importantly, it should be noted that, in contrast withthe Internet, no routing is necessary and thus the invention providesimportant advantages in respect of efficiency, speed, processing andrequired resources.

The process is as follows

-   -   1. The end user inputs keywords into the browser-wallet search        bar.    -   2. The browser-wallet sends the keyword query to a third-party        SE.    -   3. The SE checks the keywords against its database and returns        ID_(node) for any Metanet nodes containing relevant content. The        third-party can also return other indexes on each node to the        user, as well as providing suggestions for related content.    -   4. The browser-wallet uses the node identity and the domain name        associated with it to construct a MURL.    -   5. The browser-wallet requests the content belonging to the        specified node from any network peer with a full copy of the        blockchain.    -   6. The network peer serves the browser-wallet with the requested        content. Because the peer has a copy of the blockchain, they        must also have a copy of the content and so only one request is        made, and it is never forwarded to other network peers.

It is emphasised that the third-party SE only has the responsibility ofindexing and maintaining records of the attributes of Metanet nodes,while the raw content data stored on the nodes is instead stored bynetwork peers (e.g. full-copy peers, miners, archives) with a full copyof the blockchain.

Content Display—Metanet Browser

The browser-wallet application emulates the same front-end capabilitiesthat any typical web-browser should provide. These functions include,but are not limited to:

-   -   1. Searching—Provide access to a search engine (SE) for locating        content.    -   2. Retrieval—Communicate with a server to facilitate the        transfer of content using a known protocol e.g. Hypertext        Transfer Protocol (HTTP).    -   3. Interpreting—Parsing raw code (e.g. in JavaScript) and        executing.    -   4. Rendering—Efficient display of parsed content to be viewed by        the end user.    -   5. User interface (UI)—Provide an intuitive interface for a user        to interact with content, including action buttons and mechanism        for user-input.    -   6. Storage—Local temporary storage capacity for caching internet        content, cookies etc., to improve repeated access to content.

In certain embodiments, the software component of the browser-walletapplication responsible for acting as a web-browser is able to performthe above functions on Metanet content embedded in the blockchain thatis both searchable (using SEs) and retrievable (from peers) using theirattributes.

Recombination, De-Compression and Decryption

In accordance with certain embodiments of the invention, the web-browsersoftware component of the browser-wallet application is able to handleall operations that need to be performed on given Metanet content. Thereare many such operations that need to be performed in general, but weassume that at least the following are executed by the application usingthe Metanet protocol and infrastructure.

-   -   Recombination—In the case that Metanet content needs to be split        up and inserted into multiple separate node transactions, the        application will request the content from all relevant nodes and        reconstitute the original content. The ordering and structure of        the splintered content can be encoded using additional flags in        each node's attributes.    -   Decompression—Where content data is stored on the blockchain in        a compressed form, it should include a flag to indicate to the        browser-wallet which standard compression scheme has been used.        The application will decompress content according to this flag.    -   Decryption—Where content is encrypted a flag should be used to        signify the encryption scheme. The application will locate a key        from its decryption key wallet (as discussed below) and decrypt        content data for use according to the encryption scheme used.

In performing these operations on content data, flags can be used tosignify to the browser-wallet that a given operation needs to beperformed. This generalises to any other operation, for which a suitable<operation_flag> can be included as part of the attributes of nodes towhich the operation applies.

Caching

The caching of local files and cookies is a common and importantfunction of typical web-browsers. The browser-wallet application alsouses local storage in a similar way in order to optionally keep a recordof ID_(node) and other node attributes that pertain to content ofinterest. This allows more efficient lookup and retrieval of contentfrom frequently-visited Metanet nodes.

The Metanet solves the problem inherent with caching internet data thatit is mutable and can be changed or censored by web-browsing softwaredepending on the provider. When caching Metanet data a user can alwayseasily verify that it is in the same state as when originally includedas an immutable record on the blockchain.

Cryptocurrency Wallet

Hierarchical Deterministic Key Management

Deterministic keys Dk are private keys initialized from a single “seed”key (See Andreas M. Antonopoulos, Chapter 5 in “Mastering Bitcoin”O'Reilly 2^(nd) Ed., 2017, pp. 93-98). The seed is a randomly generatednumber that acts as a master key. A hash function can be used to combinethe seed with other data, such as an index number or “chain code” (seeHD Wallets—BIP-32/BIP-44), to derive deterministic keys. These keys arerelated to one another and are fully recoverable with the seed key. Theseed also permits the easy import/export of a wallet between differentwallet implementations, giving an additional degree of freedom if theuser wishes to use an external wallet in conjunction with the Metanetbrowser-wallet.

A hierarchical deterministic (HD) wallet is a well known derivationmethod of deterministic keys. In HD wallets, a parent key generates asequence of children keys, which in turn derive a sequence ofgrandchildren keys, and so on. This tree-like structure is a powerfulmechanism for managing several keys.

In a preferred embodiment, a HD wallet can be incorporated into theMetanet architecture illustrated in FIG. 16. Advantages of using HDwallets include:

-   -   1. Structure Additional organizational meaning can be expressed        using different branches of subkeys for different purposes. For        example, a user could dedicate different branches (and their        corresponding subkeys) to different types of data.    -   2. Security Users can create a sequence of public keys without        the corresponding private keys, making HD wallets functional in        a receive-only capacity and suitable for use on insecure        servers. Also, since fewer secrets need to be stored there is a        lower risk of exposure.    -   3. Recovery If keys are lost/corrupted then they can be        recovered from the seed key.

Native (Internal) and External Wallet Support

Advantageously, embodiments of the invention can directly merge thefunctionality of traditional web-browsers with one or morecryptocurrency wallets. This is fundamentally how the Metanet combinesthe payment for “internet” content with its delivery to the end user.

To achieve this, embodiments of the browser-wallet may have a dedicated,in-built software component that operates as a cryptocurrency wallet.This wallet is native the application itself and can be used to managecryptocurrency private keys and authorise transactions as payment forMetanet content within the browser-wallet itself.

This means that the browser component of the application can prompt thewallet component to authorise a payment that is required—by purchasing adecryption key, access token or otherwise—to view Metanet content. Theapplication does not need to invoke an external third party to processthe payment, and thus the Metanet content of interest is consumed by theapplication and paid for in-situ.

External Wallets

The same advantages and functionality can be achieved by embodiments ofthe application if a user wishes to instead manage or keep theircryptocurrency private keys on an external wallet (software or hardware)or even use multiple wallets. This may be performed in lieu of, or inconjunction with, the application's native wallet.

In such embodiments, the application establishes a link or pairing withan external wallet(s), and synchronises with it, but does not storeprivate keys in the browser-wallet itself. Instead, when the browsercomponent prompts a payment to be made for content, the applicationrequests an authorisation by digital signature from the external walletof choice. This authorisation is made by the user and the browser-walletcan broadcast the transaction and view the paid content.

Reading and Writing Metanet Transactions

An intrinsic advantage of the Metanet is that it uses the samedata-structure—the blockchain—to record both payments and content data.This means that software wallets can be used to write content data tothe Metanet infrastructure in addition to creating transactions that arepurely based on the exchange of cryptocurrency.

The native wallet built-in to the application is able to writetransactions to the blockchain that are more complex than typicalsimplified payment verification (SPV) clients—see hapshttps://bitcoin.org/en/glossary/simplified-payment-verification. Thewallet allows users to choose to write a Metanet node transaction to theblockchain directly from the application by selecting content data, fromtheir computer, to be embedded in the blockchain.

As the browser-wallet application has a user interface (UI) it allowsfor the wallet component to create and broadcast transactions thatinclude content data that has be constructed either in thebrowser-component or on the user's computer beforehand. This capabilitywould be far more difficult to achieve for a purpose-built wallet tohandle on its own.

Access Key/Token Wallet

Recall from above that, built in to the Metanet protocol, is the abilityto encrypt content using an ECC keypair or AES symmetric key, and theability purchase the corresponding decryption key or token. We willrefer to these as access keys or access tokens.

Such keys/tokens grant the user permission to view or edit content(either single use or multi-instance use) and play a distinct role fromkeys that control the users cryptocurrency wallet (although the same keymay be used for both purposes if desired). For this reason, it isadvantageous to introduce a new wallet, separate from the application'snative cryptocurrency wallet, that is used for storing and managingaccess keys and tokens.

One can also introduce the notion of timed access to Metanet content byallowing access keys/tokens to be burned after a certain time period.This can be achieved by requiring that access keys/tokens are stored ina Trusted Execution Environment (TEE) and are not directly accessible tothe user.

The fact that access keys/tokens may be “burned” is also a motivatingfactor for not storing them in the cryptocurrency wallet to ensure thereis no risk of cryptocurrency private keys being burned.

In a similar way to the cryptocurrency wallet, decryption keys andaccess tokens can be stored and managed deterministically to facilitateefficient handling and deployment. Decryption keys (e.g. ECC privatekeys) can be generated and recovered by subsequent additions to a masterkey, while access tokens can be reconstructed using a hash chain that isseeded by some initial token.

It is important to make the distinction here that the cryptocurrencywallet handles the deterministic key generation for key pairs that areused in transacting with other users and creating new Metanet nodes,whereas a key/token wallet(s) handles keys and tokens that have beenpurchased by the cryptocurrency wallet.

Block Height Permissioning

Timelocks can be included in the bitcoin script language to enable blockheight permissioning. The op_code OP_CHECKLOCKTIMEVERIFY (CLTV) sets theblock height at which a transaction output (UTXO) is permissible forspending.

The advantages of block height permissioning are twofold:

-   -   1. Version control—In the Metanet Protocol, the newest version        of a node can be identified from the node at the greatest block        height. The browser-wallet can be set up to only display the        most recent version of a file by block height, allowing        proof-of-work version control.    -   2. Timed access—The Browser-wallet application can periodically        burn the decryption keys atomically purchased by the user. This        ensures that viewers can only access content data during the        time period for which they have paid. Cloning of the decryption        keys can be prevented by storing them in a trusted execution        environment (TEE). Moreover, the atomic swap involves the        purchase of a deterministic key Dk (for decryption of the        content data). Although this deterministic key is publicly        visible, the TEE can be used to sign for the combination of Dk        and a securely enclaved private key.

The browser-wallet can be arranged to synchronise with the current stateof the blockchain in order to use block height as its own proxy fortime, rather than relying on any external clock or third-party timeoracle.

Bypassing Web-Servers

The invention allows a new mechanism for a browser (client) and a webserver to communicate and exchange information over the distributed peerinternet that bypasses domain name system (DNS) servers and typicalnetwork routing procedures. Seehttp://www.theshulers.com/whitepapers/internet_whitepaper/. Theinvention provides a new network architecture, from which thebrowser-wallet application can be served content, comprising peers thatmaintain a full-copy of the blockchain.

Local Full-Copy Peers

Consider a system of local peers in each geographical area e.g.postcode, town, city. We assume that within this local network at leastone peer maintains a full-copy of the blockchain, which we will refer toas a Local Full-Copy Peer (LFCP). For our purposes, an LFCP need onlystore the blockchain transactions that include the Metanet flag, but wedo not limit them to this.

All users default to sending ‘get’ requests to LFCPs. As the peersmaintain a complete and up-to-date copy of the entire blockchain, allrequests can be served because any node ID that is queried will beavailable to the LFCP. Note that a Metanet search engine may also act asan LFCP if the SE is powerful and large enough to both store Metanetcontent and perform the main functions of a typical SE.

In the simplest case, every LFCP will have the same storage and diskspace overheads as they will all need to be able to store the fullblockchain (around 200 GB at the time of writing). The distinctionbetween each LFCP is that they should scale their capability to respondto the demands of local requests from Metanet users. So, if each Metanetuser in the world queries their closest LFCP by default, each LCFPshould aim to scale in their operational capacity to meet their localdemand. Densely-populated areas like cities will require LFCP operationscomprising of many clustered servers, while sparser areas like smalltowns will require smaller LCFP operations.

It is important to note that the disk space requirement is universal,while the CPU requirement for each LFCP adapts to local network demand.This is an example of an adaptable network, such as Freenet—seehttps://blockstack.org/papers/.

One advantage of such a system is that users only need to make a single(local) connection to their LFCP when retrieving the content associatedwith a given ID_(node). There is no need for the LFCP to forward therequest to other peers as they are guaranteed to be able to serve therequired content themselves.

The Metanet provides many advantages over the internet—such asdecentralisation and deduplication—that are similar to otherpeer-to-peer (P2P) file-sharing services like IFPS. However, the Metanetimproves on these existing P2P models by ensuring immutability and,crucially, removing the need to flood the network with requests forgiven content.

The Metanet infrastructure is also robust to the compromise of any oneLFCP by employing a network of these peers. This means that if a LFCP isdisabled then the end user simply defaults to using their next nearestLFCP. This can be made more efficient if LFCPs communicate with eachother to indicate which nearby peers are below or above capacity interms of requests at any given time. This can allow users to send theirrequest to the most appropriate peer and establish dynamic equilibria inthe request distribution between nearby LFCPs.

Global Full-Copy Peers

We now consider a scenario when the universal disk space requirementbecomes too great for smaller peers, which may happen as the Metanetportion of the blockchain scales and grows with adoption.

In this case smaller LFCPs should use their disk space capacity to storeMetanet node transactions based on a popularity system (there areexisting techniques for ranking content by request volume and nature).This means that LFCPs now tailor both their CPU (for request handlingability) and their storage allocation (for content-serving ability) tosuit their local geographic demands both in volume and nature ofcontent.

In order to address the fact that LFCP are now unable to store allMetanet transaction content the concept of a Global Full-Copy Peer(GFCP) can be utilised. A GFCP is a full-copy peer that has thefollowing properties:

-   -   1. A GFCP grows its disk space capacity in order to maintain a        full-copy of the blockchain at all times.    -   2. A GFCP has substantial CPU resources such that it can handle        significantly more requests than an LFCP. A global full-copy        peer should be able to handle a sudden increase in demand should        many LFCPs become compromised.

There are two main functions of a GFCP. First, to act as a failsafe foruser requests of Metanet content in times of overflow requests fromLFCPs. Second, GFCPs act as archive peers to store all Metanet contentmined historically, which ensures that any Metanet node content can beaccessed even if many LFCPs omit some content from their local storageprovisions.

Global Data Banks

The concept of a GFCP is a powerful one and illustrates how the overallarchitecture of the Metanet provides a solution to an existing problem;that of creating all-encompassing, global data banks.

Before now, it has not been possible to safely construct a universal andglobally-accessible data bank because it would need to be maintained bya central authority. This central authority injects both a point offailure and of trust into the system. Crucially, if one organisation isrelied upon to store and maintain all internet data then we need totrust the facts that they are doing so correctly and legitimately,without corrupting the information.

With the Metanet infrastructure, we have effectively removed both ofthese problems, those of trust and of centrality, from the concept of aglobal data centre. Now, such a GFCP can be created because they areonly relied upon to provide the required disk space for storage and notto verify and authenticate the information to be stored.

With the Metanet, the process of verifying what is stored is done byminers and hence universal, global data banks can be trusted becausethey cannot corrupt blockchain information. The GFCP does not need to betrusted and need only provide storage. The fact that all GFCPs can storethe same information, that is always verifiable and provable against theblockchain itself, means that it can be replicated across many suchGFCPs. This means me have also solved the issue of having a single pointof failure by enabling many global data banks to exist in parallel andprovably store the same information.

FIG. 17 shows a system of two LFCPs and one GFCP and illustrates howeach peer can support the other in a network that is robust to thecompromise of individual peers.

The aspects of the invention which can be implemented in embodiments ofthe browser-wallet application described above provide numerousdistinguishing features and advantages over the prior art, including butnot limited to:

-   -   1. Deterministic keys—Hierarchical deterministic key management        for both cryptocurrency and Metanet addresses is performed in        the same wallet component of the application. This allows        organisation of keys with multiple functions that reduces their        storage requirements and enables key recovery.    -   2. Payment mechanism—The application allows consumers to pay        merchants directly without needing to point to another        application or third-party payment service that would        conventionally authenticate and provide trust. This allows the        purchase and delivery of digital content to take place via the        same blockchain platform. The application inherits the        advantages of bitcoin payments including low value exchanges or        more complex transactions involving multiple parties.    -   3. Bypassing web-servers—The application facilitates the        bypassing of traditional web-servers, which would conventionally        process a high volume of traffic, requests and routing. This is        because the application need only request content from a single        LFCP, which is guaranteed to serve the user without needing to        forward the request to other LFCPs. This reduces the overall        traffic volume as well as the completion time of each request.    -   4. Timed access—The application facilitates timed access to        content by synchronising with the blockchain and using it to        enforce access permissions based on its current state. This        removes the need for third party services to monitor a users'        privileges over time while protecting the rights of the original        owner.

Use Case—Decentralised App Store (Swapp Store)

The first use case presented here (for illustrative purposes only) forthe Metanet architecture is for the decentralised payment for anddistribution of applications (apps).

We consider a scenario in which an app developer Alice and a consumerBob wish to transact with each other. This transaction will take theform of an atomic swap in which money is exchanged for a secret key thatgrants Bob access to the application data. The encrypted applicationdata is already public as part of a Metanet node transaction.

An atomically-swapped application is known as a Swapp. A third-partyplatform (Swapp store) may be used for cataloguing and advertisingapplications that exist on the Metanet, but the payment for and transferof the access key to a user such as Bob does not need to involve anythird party and can be done directly between merchant and consumer.

The following section details a process that may be used for buying andselling Swapps from the creation of an app by Alice to its deployment byBob. Throughout the process, Alice and Bob will use their respectivebrowser-wallets to interact with the Metanet.

Publishing

-   1. Alice writes an application. The data that constitutes this    application is the content denoted by <App>. She also encrypts it    sa<e(App)> using a secret key S_(k).-   2. Alice creates a node transaction, ID_(AliceApp) to set up her    first Metanet domain (tree). She generates    1AliceAppHtKNngkdXEeobR76b53LETtpy (P_(AliceApp)) to be used as the    node address.    -   3. Alice then creates children of the first node to form a tree        that corresponds to a Metanet library of her applications.        Alice's tree domain is shown in FIG. 18.        -   One of the leaf nodes on this tree is the node corresponding            to her application <App> with index ID_(App). In this node,            Alice inserts the encrypted application data <e(App)> into            the input script (scriptSig) of the node. The app data is            encrypted using the Koblitz method using a secret key s_(k).        -   This node transaction is shown below.

TxID_(App) Input Output < Sig P_(Puzzle)> <P_(Puzzle)> <e(App)>OP_RETURN <Metanet Flag> <P_(App)> OP_DROP <TxID_(Puzzle)>

-   -   4. Alice broadcasts ID_(AliceApp), P_(AliceApp) and domain name        ‘AliceApp’ publicly. This can be via social media, an internet        website or by using a third-party Metanet website.

Purchasing

-   1. Bob wants to download a puzzle game and sees Alice's app listed    on a Metanet website (Swapp store) that he views on his    browser-wallet.-   2. Bob then communicates with Alice, using information from the    website, and sets up an atomic swap. The swap is designed such that    Bob will pay an agreed price in Bitcoin to Alice and Alice will    reveal the secret key s_(k) or neither event occurs.-   3. The atomic swap is completed and Bob's browser-wallet stores the    secret key s_(k) in its access key/token wallet.

Deployment

Bob now has the key s_(k) that will allow him to decrypt the applicationdata Alice published previously. In order to download the app and deployit Bob does the following.

-   -   1. Bob uses a Metanet search engine (SE) to find the MURL        associated with the encrypted app data <e(App)>. He uses the        keywords ‘AliceApp’ and ‘App’ as input to the search bar in his        browser-wallet. The third-party SE resolves the query and        returns the following MURL:        -   mnp://aliceapp/games/puzzle/app        -   This locator corresponds to the unique Metanet node ID_(App)            which includes the encrypted app data in its input script.    -   2. Bob's browser wallet receives this MURL and sends a request        to the nearest appropriate LFCP. This peer serves Bob with the        requested data <e(App)>.    -   3. The browser-wallet processes the data according to the        attributes of ID_(App). This includes using the secret key s_(k)        to decrypt the application data and process <App>.    -   4. Bob downloads the application <App> from his browser to his        computer. Bob can now deploy the application locally without        having to re-purchase access.

FIG. 19 illustrates the entire process outlined in the aboveillustrative use case. The flow chart shows two action branches, Alice's(starting on the left hand side) and Bob's (starting on the right handside). The branch corresponding to Alice shows the initial publishingphase and Bob's shows the phase of setting up the purchase via atomicswap.

On Bob's branch, he broadcasts the following transaction TxID_(Bob) asthe atomic swap set-up phase:

TXID_(Bob) Inputs Outputs Value Script Value Script x BCH < Sig P_(B)><P_(B)> x BCH [Private Key Puzzle P_(k), r₀] [CheckSig P_(A)]

-   -   In this transaction, the output is locked with a private key        puzzle that requires the secret decryption key s_(k) to be        revealed to Bob in order for Alice to spend. Alice and Bob's        branches in this diagram converge at the point where Alice        successfully completes the atomic swap transaction. This is        achieved when Alice broadcasts the transaction TxID_(Alice):

TxID_(Alice) Inputs Outputs Value Script Value Script x <Sig P_(A)><P_(A)> <Sig P₁, r₀> x [CheckSig P_(A)] Bitcoin <P₁> Bitcoin

As soon as this transaction is broadcast, Alice and Bob's actionbranches diverge once more. Alice receives payment of x Bitcoin whileBob receives the secret decryption key s_(k) and is able to retrieve anddecrypt Alice's application from the Metanet.

Turning now to FIG. 20, there is provided an illustrative, simplifiedblock diagram of a computing device 2600 that may be used to practice atleast one embodiment of the present disclosure. In various embodiments,the computing device 2600 may be used to implement any of the systemsillustrated and described above. For example, the computing device 2600may be configured for use as a data server, a web server, a portablecomputing device, a personal computer, or any electronic computingdevice. As shown in FIG. 20, the computing device 2600 may include oneor more processors with one or more levels of cache memory and a memorycontroller (collectively labelled 2602) that can be configured tocommunicate with a storage subsystem 2606 that includes main memory 2608and persistent storage 2610. The main memory 2608 can include dynamicrandom-access memory (DRAM) 2618 and read-only memory (ROM) 2620 asshown. The storage subsystem 2606 and the cache memory 2602 and may beused for storage of information, such as details associated withtransactions and blocks as described in the present disclosure. Theprocessor(s) 2602 may be utilized to provide the steps or functionalityof any embodiment as described in the present disclosure.

The processor(s) 2602 can also communicate with one or more userinterface input devices 2612, one or more user interface output devices2614, and a network interface subsystem 2616.

A bus subsystem 2604 may provide a mechanism for enabling the variouscomponents and subsystems of computing device 2600 to communicate witheach other as intended.

Although the bus subsystem 2604 is shown schematically as a single bus,alternative embodiments of the bus subsystem may utilize multiplebusses.

The network interface subsystem 2616 may provide an interface to othercomputing devices and networks. The network interface subsystem 2616 mayserve as an interface for receiving data from, and transmitting data to,other systems from the computing device 2600. For example, the networkinterface subsystem 2616 may enable a data technician to connect thedevice to a network such that the data technician may be able totransmit data to the device and receive data from the device while in aremote location, such as a data centre.

The user interface input devices 2612 may include one or more user inputdevices such as a keyboard; pointing devices such as an integratedmouse, trackball, touchpad, or graphics tablet; a scanner; a barcodescanner; a touch screen incorporated into the display; audio inputdevices such as voice recognition systems, microphones; and other typesof input devices. In general, use of the term “input device” is intendedto include all possible types of devices and mechanisms for inputtinginformation to the computing device 2600.

The one or more user interface output devices 2614 may include a displaysubsystem, a printer, or non-visual displays such as audio outputdevices, etc. The display subsystem may be a cathode ray tube (CRT), aflat-panel device such as a liquid crystal display (LCD), light emittingdiode (LED) display, or a projection or other display device. Ingeneral, use of the term “output device” is intended to include allpossible types of devices and mechanisms for outputting information fromthe computing device 2600. The one or more user interface output devices2614 may be used, for example, to present user interfaces to facilitateuser interaction with applications performing processes described andvariations therein, when such interaction may be appropriate.

The storage subsystem 2606 may provide a computer-readable storagemedium for storing the basic programming and data constructs that mayprovide the functionality of at least one embodiment of the presentdisclosure. The applications (programs, code modules, instructions),when executed by one or more processors, may provide the functionalityof one or more embodiments of the present disclosure, and may be storedin the storage subsystem 2606. These application modules or instructionsmay be executed by the one or more processors 2602. The storagesubsystem 2606 may additionally provide a repository for storing dataused in accordance with the present disclosure. For example, the mainmemory 2608 and cache memory 2602 can provide volatile storage forprogram and data. The persistent storage 2610 can provide persistent(non-volatile) storage for program and data and may include flashmemory, one or more solid state drives, one or more magnetic hard diskdrives, one or more floppy disk drives with associated removable media,one or more optical drives (e.g. CD-ROM or DVD or Blue-Ray) drive withassociated removable media, and other like storage media. Such programand data can include programs for carrying out the steps of one or moreembodiments as described in the present disclosure as well as dataassociated with transactions and blocks as described in the presentdisclosure.

The computing device 2600 may be of various types, including a portablecomputer device, tablet computer, a workstation, or any other devicedescribed below. Additionally, the computing device 2600 may includeanother device that may be connected to the computing device 2600through one or more ports (e.g., USB, a headphone jack, Lightningconnector, etc.). The device that may be connected to the computingdevice 2600 may include a plurality of ports configured to acceptfibre-optic connectors. Accordingly, this device may be configured toconvert optical signals to electrical signals that may be transmittedthrough the port connecting the device to the computing device 2600 forprocessing. Due to the ever-changing nature of computers and networks,the description of the computing device 2600 depicted in FIG. 20 isintended only as a specific example for purposes of illustrating thepreferred embodiment of the device. Many other configurations havingmore or fewer components than the system depicted in FIG. 20 arepossible.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe capable of designing many alternative embodiments without departingfrom the scope of the invention as defined by the appended claims. Inthe claims, any reference signs placed in parentheses shall not beconstrued as limiting the claims. The word “comprising” and “comprises”,and the like, does not exclude the presence of elements or steps otherthan those listed in any claim or the specification as a whole. In thepresent specification, “comprises” means “includes or consists of” and“comprising” means “including or consisting of”. The singular referenceof an element does not exclude the plural reference of such elements andvice-versa. The invention may be implemented by means of hardwarecomprising several distinct elements, and by means of a suitablyprogrammed computer. In a device claim enumerating several means,several of these means may be embodied by one and the same item ofhardware. The mere fact that certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage.

1. A method of storing data on a blockchain, the method comprising:generating a blockchain transaction having at least one first input andor at least one first output containing first data to be stored on theblockchain, and at least one second input and or at least one secondoutput containing second data representing at least one attribute ofsaid first data, wherein at least one said second input and or at leastone said second output is separate from the or each said first input andor first output.
 2. A method according to claim 1, wherein the firstdata is contained in a plurality of said first inputs and or said firstoutputs.
 3. A method according to claim 1, wherein said second dataincludes data relating to recombination of said first data.
 4. A methodaccording to claim 1, wherein at least one said second input and or atleast one said second output includes indication data indicating thatthe transaction includes said first data.
 5. A method according to claim1, wherein the second data represents at least one attribute of saidfirst data, being at least one of data type, data encryption scheme,data compression scheme, indexing information, permission information,encoding information, keyword information or searching information ofsaid first data.
 6. A method according to claim 1, wherein the firstdata is contained in at least one said first output.
 7. A methodaccording to claim 1, wherein at least one said first and/or secondoutput includes a script opcode for marking an output as invalid forsubsequent use as an input to a subsequent transaction.
 8. A methodaccording to claim 1, wherein at least one said first output isredeemable by means of at least one key corresponding to a respectivedigital signature applied to said first data.
 9. A method according toclaim 1, wherein a digital signature is applied to said first data. 10.A method according to claim 9, wherein at least one said digitalsignature is based on a cryptography system having a public-private keypair, wherein a private key of the public-private key pair is based on aplurality of prime numbers and a corresponding public key is based on aproduct of a plurality of said prime numbers.
 11. A method according toclaim 10, wherein at least one said digital signature is a Rabinsignature.
 12. A method according to claim 1, further comprisingapplying data compression to said first data and/or said second data.13. A computer-implemented system comprising: a processor; and memoryincluding executable instructions that, as a result of execution by theprocessor, causes the system to perform any embodiment of the method asclaimed in claim
 1. 14. A non-transitory computer-readable storagemedium having stored thereon executable instructions that, as a resultof being executed by a processor of a computer system, cause thecomputer system to at least perform an embodiment of the method asclaimed in claim
 1. 15. A computer-implemented system comprising: aprocessor; and memory including executable instructions that, as aresult of execution by the processor, causes the system to perform anyembodiment of the method as claimed in claim
 2. 16. Acomputer-implemented system comprising: a processor; and memoryincluding executable instructions that, as a result of execution by theprocessor, causes the system to perform any embodiment of the method asclaimed in claim
 3. 17. A computer-implemented system comprising: aprocessor; and memory including executable instructions that, as aresult of execution by the processor, causes the system to perform anyembodiment of the method as claimed in claim
 4. 18. A non-transitorycomputer-readable storage medium having stored thereon executableinstructions that, as a result of being executed by a processor of acomputer system, cause the computer system to at least perform anembodiment of the method as claimed in claim
 2. 19. A non-transitorycomputer-readable storage medium having stored thereon executableinstructions that, as a result of being executed by a processor of acomputer system, cause the computer system to at least perform anembodiment of the method as claimed in claim
 3. 20. A non-transitorycomputer-readable storage medium having stored thereon executableinstructions that, as a result of being executed by a processor of acomputer system, cause the computer system to at least perform anembodiment of the method as claimed in claim 4.